I'm sure there will be varying opinions on this but, I try to keep these discussions out of the exit interview to keep that meeting short and to the point. Ideally, the department with this finding has already been informed, prior to the exit, of the matter. Typically, if they know the "why", they will offer it up immediately. Other times, it requires research. Eventually, the root cause should be identified in their formal written response, but, I agree that if the discussion can happen in the field, it encourages open communication between the team and the campus. Additionally, it helps the audit team evaluate the potential risk as it relates to whether or not the problem is likely to be occurring at multiple sites or if it seems to be more of an isolated occurrence.